Smectic- Cα* phase with two coexistent helical pitch values and a first-order smectic- Cα* to smectic- C* transition

Previous results from Kundu using dielectric relaxation have suggested a reentrant antiferroelectric-ferroelectric-antiferroelectric transition in the compound LN36. Our comprehensive studies of this compound using differential optical reflectivity, nonadiabatic scanning calorimetry, null transmission ellipsometry, and resonant x-ray diffraction show that in fact LN36 exhibits the usual phase sequence for chiral smectic liquid crystals: Sm A* -Sm Cα* -Sm C* -Sm C FI1 * -Sm CA*. Moreover, the Sm Cα* -Sm C* transition is a first-order transition, characterized by a discontinuous change in the helical pitch. At temperatures just above the Sm Cα* -Sm C* transition, two different values for the helical pitch are simultaneously observed for the first time.